JPH0499185A - Photoetching method - Google Patents

Abstract

PURPOSE:To narrow the pitch between the terminals of a lead frame, etc., by preventing side etching with an electrodeposited positive type photoresist at the time of photoetching and carrying out deep and narrow etching. CONSTITUTION:A required pattern is formed on the surface of a body to be etched with an etching resist and the body is etched. This etching is suspended and a positive type photoresist (h) is electrodeposited. Only the bottom (a) of the etched part is exposed with a photomask (g) and disclosed by development and then etching is carried out again. Side etching is prevented and deep etching is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses an electrodeposited photoresist to prevent side etching during photoetching and enables deep and narrow etching, thereby making it possible to manufacture products using a high-density photoetching method. This made it possible.

In recent years, with the development of electronics, it has become increasingly necessary for electronic components to be highly integrated, multi-functional, and highly dense. Photoetching is also required for high-density printed wiring boards such as IC lead frames and chip-on-boards. It is manufactured using.

However, photo-etching is usually carried out using a photoresist as shown in (1) Figures A and B, but in this case, etching is not only done on the lower bottom surface a but also on the side surfaces, so that the etching of the member to be etched is As the thickness increases, the amount of etching on the side surfaces (side etching) increases, and (2) as shown in Figures A and B, the etching width becomes significantly wider than the planned etching. If a photomask is prepared with this amount of side etching in mind, the width of the etching slit will become small, which will limit the resolution and etching ability of the photoresist, making it impossible to perform narrow and deep etching.

Until now, methods have been devised for etching deep engravings, such as using etching liquids with a small amount of side etching, side etch inhibitors, and increasing the etching shower pressure. be.

Side etch inhibitors are rarely used for reasons such as cost, drainage treatment problems, and lack of sufficient side etch prevention effects. Furthermore, the method of increasing the shower pressure has the problem that as etching progresses and the overhang of the photoresist becomes large, the photoresist tends to break due to the shower pressure, making it impossible to perform accurate etching.

Bonding for IC mounting etc. requires a certain amount of circuits and terminals, and if you try to increase the number of terminals within the same size, it is necessary to narrow the width between the circuits, but the conventional manufacturing method It is said that when the material thickness is 0.151111, the etching slit width is limited to about 0.1fl.

In order to solve the above problems, the present invention uses a photoresist as shown in Figure (3), stops etching when the amount of side etching is small, and uses a positive electrodeposition photoresist as shown in Figure (4). The photoresist is deposited on the entire surface including the inner wall of the hole, exposed only to the bottom of the etched area using a photomask, and developed.
) As shown in the figure, the side walls of the etched area can be covered with resist, leaving only the bottom surface exposed.

When etching is then performed for the second time, since the sides of the etched area are covered with photoresist, etching progresses only on the bottom side. This makes it possible to perform etching approximately twice as deep as the conventional etching width.

By repeating this operation, deeper etching can be achieved.

The use of positive type electrodeposited photoresist in the present invention is as follows:
It is only possible to form a thin and uniform film thickness (2 μ to 10 μm) on the side and bottom surfaces of the concave etched part where etching is performed halfway, and this is not possible with depping, etc. It is impossible to form a film of uniform thickness due to the formation of deposits.

If the film is not thin enough, the narrow etching slit will not allow sufficient light to reach the bottom surface, and the bottom surface will not be exposed through exposure and development.

Furthermore, since the resist must be thick enough to withstand etching, the formation of a uniform and thin resist film is an essential condition.

Using a positive type photosensitive liquid, you can first use a photomask with a slit width slightly narrower than the width of the etched sides, and expose only the bottom surface without exposing the side walls to light using a parallel light exposure machine. By exposing the resist to light and developing it, the sides can be covered with resist and only the bottom can be exposed.

If a photopolymerizable negative type was used, it would be technically impossible to expose only the sides and the bottom, but this technology would only be possible using a photodegradable positive type photosensitive liquid.

It is best to use parallel light for exposure, but considering the angle of incidence of light on the resist, it is possible to leave a resist film only on the sides even if scattered light is used by adjusting the width of the photomask slit and the exposure amount. It is possible.

As an example of the effectiveness of the present invention, it is possible to narrow the slit width for etching thick materials, thereby dramatically reducing the pitch between terminals of lead frames and the like.

If this allows the terminal pitch of the lead frame to be close to the 130μ pitch, which is said to be the limit value for IC inner bonding using a nail head, the IC chip size can be reduced, and the cost of the IC chip can be greatly reduced. Can be lowered.

Furthermore, since the length of the bonding wire can be shortened, it can prevent the wire from collapsing and greatly improve reliability, which has great benefits.

[Brief explanation of drawings]

In each figure, A indicates chemical milling, and B indicates a printed wiring board. Figure 1: Cross-sectional view of the etched part during etching, Figure 2:
Figure 3: A cross-sectional view of the etched area after etching has been completed. FIG. 5 is a cross-sectional view of the etched portion, the bottom surface of which has been exposed and developed, and FIG. 6 is a cross-sectional view of the etched portion that has been etched for the second time. Symbol a, bottom surface, b, side surface, C, photoresist,
d, metal, e, insulating laminate, f, light beam, g,
Photomask, h, positive type electrodeposited photoresist coating Figure 3 Figure 1 Figure 5 1゜2゜3゜Indication of the case 1990 Patent application No. 208925 Name of the invention Photo etching method Related Applicant's address W Taiwan 1 U City Bar 1 De 3-4 October 30, 1990 Procedural amendment (method) Sennarizu 1''・1+:', f1 Submitted May 2, 1991 Toshido Uematsu

Claims (2)

[Claims] (1) Form the required pattern on the surface of the object to be etched with an etching resist, stop the subsequent etching process midway through, deposit a positive type photoresist using the electrodeposition coating method, and apply the photoresist to the side wall of the etched area using the exposure phenomenon. A photo-etching manufacturing method that prevents side etching and enables deep etching by restarting etching after forming an etching resist film. (2) Photo-etched products such as lead frames, printed wiring boards, chemical milling, sheet coils, etc. manufactured using the above-mentioned photo-etching manufacturing method.